“No President of the United States, no matter party or political ideology, has the authority to unilaterally start a war. While the president has the authority under the War Powers Act to respond when the U.S. is under attack or in imminent danger, such circumstances did not exist with regard to Syria,” Mr. Lee, Utah Republican, said in a statement on Twitter.

“Promoting regional stability, mitigating humanitarian catastrophe, and deterring the use of chemical weapons might be important foreign policy goals, but if they are to be pursued with military force, a president must first seek congressional authorization,” he added.

Mr. Lee released the statement after the White House said there was sufficient constitutional authority for the strike. The Trump administration launched the airstrike attack on Friday evening without obtaining a new Authorization for Use of Military Force, or AUMF, as some lawmakers had called for.

Last week, he joined fellow Sen. Rand Paul, Kentucky Republican, in calling for the administration to obtain authorization from Congress prior to the strike.

I issued the following statement in response to a White House letter purporting to identify sufficient constitutional authority for Friday night’s attack in Syria: pic.twitter.com/Sn4Z41IPuI